In the broadcast industry, it is an inherent problem to direct programs at desired audiences. Programs, as used herein, include multimedia presentations having video and audio components. Programs reaching targeted audiences can have increased economic value. In the prior art, broadcasters generally have little control over the distribution of their programs. For example, the potential audience of a program is generally defined by the reach of the broadcast signals.
For conventional terrestrial broadcasts, the reach of the program signals may be a circular region around the transmitter tower. For cable systems, the span of the broadcast is determined by the lay of the cables. For satellite broadcasts, the geography covered can be quite large. However, each of these modalities usually broadcasts to diverse demographic audiences located within distinct localities or communities of the broadcast region.
In the prior art, the selection of the audience is primarily done by carefully matching advertisements, and other inserted content with a continuing base program. The hope is that audiences are more likely to watch inserted advertisements which closely match the base program content. For example, household products are frequently marketed during soap operas. Likewise, advertisements for motor products are usually matched with motor sports programs. However, the broadcaster has no way to separate audiences interested in new luxury automobiles from those simply interested in motor additives and repair tools.
Traditional programs broadcast as analog signals are interrupted at epochs chosen by the originator of the program stream. Advertisements, public service information, and other content fill the interruptions. In some advanced broadcast networks, the originator of the program indicates that a "slot" is available to a downstream distributor. Local broadcasters can then fill the slot with an advertisement which exactly matches the length of time of the gap made available by the originator. However, segmentation under this approach is still largely limited by geography. All the viewers of the program receive the same single program stream where the continuing base program and short subject fillers, from a technical point of view, are indistinguishable and tightly coupled.
More recently, broadcasters have started to upgrade their analog networks to carry programs encoded in digital form. In digital form, the program stream is partitioned into one or more elementary streams. For example, a composite program stream may include a video stream, and possibly multiple audio streams. The elementary streams are encoded and compressed according to an industry standard, for example, the Motion Pictures Expert Group's standards MPEG-1 or MPEG-2. The encoded digital signals of the program stream can further be encapsulated into transport packets for ease of handling by the network.
The network can include circuits to transport the program signals to the audiences. The circuits may be a television channel, a cable channel, a satellite channel, or a virtual circuit of an asynchronous mode (ATM) telephone network. Recently, interactive television and video-on-demand type of networks may allow a greater amount of control over matching program content with audiences. However, interactive program distribution requires two-way (duplex) communication on the network. Duplex communication may not always be possible with extant networks, and generally uses substantially more complex and expensive equipment at the transmitter and receiver sites. It is desired to precisely broadcast program signals to well identified target audiences without unduly increasing the complexity of extant broadcast networks, and the processes and equipment used to originate and receive the programs.